Experimental (a) and calculated (b) extinction spectra of aggregated Ag hydrosol (within the surface plasmon absorption band) before and after irradiation and photomodification of aggregates (solid line) and after the end of laser pulse (dash line). Spectrum in panel (a) was obtained in 10 min, spectrum in panel (b) in 20 ns after the pulse. In panel (a), the pulse energy density is 8 mJ/cm², λ = 532 nm, pulse duration τ = 15 ns, the number of pulses over a sample 1 cm × 4 cm is 100; in panel (b), λ = 600 nm, τ = 20 ps, 1 − initial spectrum, 2 − spectrum after the pulse, 3 − the difference between spectra 1 and 2. The inset shows schematic draft of photomodification of two-particle dimer (marked dark) in the fragment of aggregate, showing the shift of particles in the dimer.